The Reducing Toxicity Action of Polyvinylpyrrolidone(PVP) in Vitrification Solutions and Its Effect on Subsequent Development of Mouse Embryos

This study investigated the effects of polyvinylpyrrolidone(PVP) on the survival and development of mouse embryos after exposure to ethylene glycol(EG) and a sucrose solution. Mouse 2-cell stage embryos were harvested from 6-to 8-wk-old ICR mice superovulated with equine chorionic gonadotrophin(eCG) and human chorionic gonadotrophin(hCG) injections 48 hours apart. They then mated with same strain male mice. M2 was selected as a basal medium for this study. To perform the exposing procedure, embryos were equilibrated with 4%(v/v) EG at 37 for 15 min, and then exposed to vitrification solutions consisting of 35%(v/v) EG, PVP(with 5, 6 and 7.5%(w/v)) and 0.4 M sucrose at 37 for 2 min. For recovery, embryos transferred serially into 300 ul of 0.5 M sucrose at room temperature for 5 min, 0.3 M sucrose at room temperature for 5 min and then M2 medium at 37 for 10 min. Embryos were washed three times and then cultured in KSOM medium under mineral oil at 37 for 96-120 hr in 5% CO2 and 95% air at maximal humidity. Survival of mouse embryos was evaluated by their general morphological appearances, like zona disruption and the existence of apoptotic blastomeres after recovery.The survival rate of the 7.5% PVP concentration group was significantly higher than the 5% and 6% PVP groups(100% vs. 73.0% and 91.0%, P < 0.05), respectively. Blastocyst formation was increased in a concentration-dependent manner. The mean cell numbers of blastocysts of each group were similar. Especially, survival rate and development of the 7.5% PVP group were similar to the control group. Our study indicated that 7.5% PVP was the most appropriate concentration for the vitrification of ICR mouse 2-cell embryos.